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#46651 - 12/30/04 03:20 AM Voltage on CATV wire  
ComputerWizKid  Offline
Member
Joined: Sep 2003
Posts: 119
Connecticut, USA
I got a shock while hooking up my cable tv to my computer and I tested it for voltage and I got 112.8VAC wall voltage is 118.2 (My House normal)I know this is not normal so how could the voltage get there? and when I connected the computer to the outlet I was greeted with A spark and a tripped breaker (Computer is grounded 3 pin plug rest of my home enterainment stuff is not)


Theres always enough room in the junction box.You just need a bigger hammer

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#46652 - 12/30/04 08:22 AM Re: Voltage on CATV wire  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
First, the coax shield was not bonded as required in Article 820, and second, something that the coax is connected to is defective and has energized the coax shield.
Note, there is one more possibility. The EGC to the computer is connected to a hot conductor and not ground.
Don


Don(resqcapt19)

#46653 - 12/30/04 05:13 PM Re: Voltage on CATV wire  
dereckbc  Offline
Member
Joined: Oct 2003
Posts: 156
Tulsa, OK
I agree with Don. Here are the steps I would follow.

1. Disconnect cable from everything in the house, then look with a volt meter to check voltage. Keep in mind a DVM has high impedance and will read false voltages on an open circuit. Either add a load like a 10K resistor or use an analog meter.
2. Make sure CATV coax is bonded to service ground where it enters the building. Check the hardware closely as it more than likely has loosened up and opened
3. Once 1&2 are completed, and there is no voltage present, connect each device one at a time and measure voltage. This will determine if any of your AV equipment is faulty.
4. That should find the problem.


#46654 - 12/30/04 09:45 PM Re: Voltage on CATV wire  
mxslick  Offline
Member
Joined: Oct 2004
Posts: 803
Atomic City, ID USA
Be sure to check any Cable boxes connected to the system. We recently went through a huge headache caused by defective cable boxes (the transformer was underrated and tended to short out to the secondary.)

Sometimes even if the box isn't really defective, poor design causes AC leakage onto the coax.

It is also possible that the voltage is coming in from outside on the system. derecbc's troubleshooting tips should pinpoint the problem.


Stupid should be painful.

#46655 - 12/30/04 10:25 PM Re: Voltage on CATV wire  
ComputerWizKid  Offline
Member
Joined: Sep 2003
Posts: 119
Connecticut, USA
The computer is properly grounded. and I found the problem my old vcr(Made in 1989) was letting line voltage on the catv in. Don't know how maybe a short or bad solder joint internly. but now everything is fine.


Theres always enough room in the junction box.You just need a bigger hammer

#46656 - 01/02/05 05:31 AM Re: Voltage on CATV wire  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
ComputerWizKid,
I do know that CATV outlets have a Capacitor in the back of the socket across the centre pin and the Braid connection, this is to isolate the system voltage from the connected equipment and vice versa.
Just check that you haven't got a Dry joint there somewhere. [Linked Image]


Let's face it, these days if you're not young, you're old - Red Green grin

#46657 - 01/02/05 07:36 PM Re: Voltage on CATV wire  
jdevlin  Offline
Member
Joined: Aug 2002
Posts: 402
welland ontario canada
You found the problem but I think your cable is not grounded properly or you would not have had the problem.


#46658 - 01/02/05 09:46 PM Re: Voltage on CATV wire  
dereckbc  Offline
Member
Joined: Oct 2003
Posts: 156
Tulsa, OK
Trumpy, any capcitor connected from center pin to shield would short out any signal on the cable.



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